Fiber reinforced thermoplastic butterfly valve element

ABSTRACT

A disk element for a butterfly valve utilizing a flattened disk-like member which typically has diametrically opposed tubular sleeve insert members mounted therein, one of such insert members being noncylindrical. The disk element is comprised of fiber reinforced thermoplastic polymer. Preferably the polymer is poly(arylene sulfide) and the fiber reinforcement is comprised of carbon or glass.

BACKGROUND OF THE INVENTION

In one aspect, the invention relates to a process for selectivelypositioning fiber reinforcement in a composite article. In anotheraspect, this invention relates to a valve element formed from acomposite material and having selectively positioned fiberreinforcement.

Thermopress molding is an extremely desirable technique to use to formarticles from thermoplastic composite materials since it allows the useof long fiber reinforcemet. Long fiber reinforcement in compositearticles generally provides highest performance properties. However,when the long fiber reinforcement is highly oriented, such as in theform of a woven mat, poor fiber flow during the molding operation leavesfiber deficient areas which are prone to premature failure.

Better fiber distribution results when random fiber mat is thereinforcement in a thermoplastic matrix. Random fibers enjoy highermobility than highly oriented fibers and become well distributedthroughout the molded articles. However, molded articles reinforced withrandom fibers are prone to failure at high stress points because randomfibers do not impart the highest performance properties. A technique forselectively providing the high stress points of articles containingrandom fiber reinforcement with oriented fibers and/or a differentloading of reinforcing fibers would be very desirable.

OBJECTS OF THE INVENTION

It is a first object of this invention to provide an article in whicheffective fiber reinforcement is selectively provided in a localizedarea.

It is another object of this invention to provide a process forselectively positioning effective fiber reinforcement in a localizedarea in a composite article.

STATEMENT OF THE INVENTION

In one embodiment of the invention, there is provided a valve elementhaving selectively positioned oriented fiber reinforcement. The valveelement is formed from a thermoplastic matrix which contains fiberreinforcement and has a disc like outer shape with an outercircumference which is usually generally circularly or cylindricallyshaped. A pair of opposed bores extend generally diametrically inwardlytoward the center of the disc from the outer circumference. At least oneof these separate opposed bores according to the invention is defined byan insert containing oriented fiber which is encapsulated by thethermoplastic matrix forming the remainder of the valve element so as tobe an integral part of the valve element. The insert is preferablycharacterized as a wound tube of fiber reinforcement in a thermoplasticmatrix. When this tube is positioned at the drive end of a butterflyvalve operating at elevated pressure, reliability of the valve fromfunctional failures is greatly increased.

In another embodiment of the invention, there is provided a process forproviding a filament reinforced insert in a thermoplastic article. Athermoplastic tubular member which is reinforced with oriented longfibers or filaments is positioned on a mandrel. The mandrel having thetubular member mounted thereon is positioned in a portion of a moldcavity. The remainder of the mold cavity is then filled with fiberreinforced thermoplastic matrix, such as in the form of prepreg blanksor injection molding compound. An article having the shape of the moldcavity with the tubular member encapsulated therein is formed. After ashort cooling period, the article is removed from the mold cavity andthe mandrel, either before or afterwards, is removed from the article,thus defining a borehole in the article which is reinforced withoriented filaments. High fiber loading and great strength can beprovided by filament winding the insert. The process is generallyapplicable to thermoplastic composite articles having a boreholepositioned therein and is especially well adapted to provide a valveelement as hereinabove discussed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial representation illustrating in exploded view avalve element incorporating certain features of the present invention.

FIG. 2 is a pictorial representation illustrating the process of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with certain features of an embodiment of the presentinvention, there is provided a valve element called out generally by thereference numeral 2 which is formed from a thermoplastic matrixcontaining fiber reinforcement and has encapsulated therein at least onetube or insert 4 of fiber reinforcement, preferably wound reinforcement,in a thermoplastic matrix so as to provide localized reinforcement to ahigh stress area of the valve element 2. Generally speaking, the valveelement 2 will have a disc like outer shape and an outer circumference 6which is generally circular or cylindrical in shape. A pair of opposedbores 8 and 10, preferably separate, extend diametrically inwardlytoward the center of the disc from the outer circumference 6. At leastone of said opposed bores 8 or 10 is defined by the insert 4. In theembodiment of the invention shown in FIG. 1, the insert 4 is positionedto define the borehole 8 and an insert 12 is positioned to define theborehole 10.

The thermoplastic matrices utilized to form the valve element and theinserts 4 and 12 are preferably, although not necessarily, of the samethermoplastic polymer. Usually, the matrix of each will be selected fromthe group consisting of polyethylene, polypropylene,polytetrafluoroethylene, polyamide and poly(arylene sulfide), andcopolymers based on such materials, since these materials arecommercially available and well suited for composite production. Mostpreferably, the matrix is formed from a poly(arylene sulfide) polymer(hereinafter PAS) because PAS has excellent corrosion resistance andstrength and can be used over a wide temperature range. The preferredPAS comprises a poly(phenylene sulfide), (hereinafter PPS), which termincludes homopolymers, copolymers, terpolymers and the like which have amelting or softening temperature of at least about 300° F. Preferred PPSusually has a melting or softening point in the range of from about 500°to about 650° F. Preferably, the PPS has a melting or softening pointsuch that it processes between about 600° F. and about 650° F. Forprocessing purposes, it is preferred that the PPS have a melt flow inthe range of from about 1 to about 500 g/10 minutes, preferably in therange of from about 25 to about 250 g/10 minutes. The melt flow of PPScan be regulated by incorporating small amounts of trichlorobenzenecomonomer into the polymerization reactor or by "curing" the polymer ofair exposure at elevated temperatures.

The fiber reinforcement used in the valve element to and the fiberreinforcement used in the insert can be selected from a wide variety ofmaterials. Preferably, the reinforcing fibers are selected from thegroup consisting of glass, carbon, aramid, metals, and ceramics,although glass or carbon fibers are preferred because they areeconomical and provide good properties in the final product. Carbonfiber provides the highest performance properties in terms of corrosionresistance and strength.

The insert is preferably fabricated by filament winding a roving of thedesired reinforcement which has been impregnated with the desiredthermoplastic resin (generally in molten form) onto a mandrel having adesired exterior shape. The roving will generally contain about 40 toabout 80 weight percent of fiber, usually 50 to 70 wt, % of continuousfiber. The insert 4 preferably has an inside surface 14 which determinesthe bore and the inside surface is preferably noncylindrically shaped soas to provide engagement with a shaft (not shown) when insertedthereinto. Where inserts are positioned in each of the opposed bores,the borehole 10 which is opposite from the noncylindrically shapedborehole 8 can be provided with a smooth and cylindrical inside surface15 by filament winding the insert 12 onto a cylindrical shaft ormandrel. The borehole 14 which is noncylindrically shaped is preferablyprovided with at least one pair of opposed flats 18 and 20 since a pairof flats will provide adequate engagement for a drive shaft and is easyto fabricate by consolidating filament windings on a suitably shapedmandrel.

FIG. 2 illustrates the process of the present invention. In accordancewith the embodiment of the invention illustrated in FIG. 2 a plastictubular member 22 to serve as the insert 4 is positioned on a mandrel 24as indicated by arrow 26. The tubular member 22 preferably has aborehole 28 therein which is noncylindrically shaped. An optional secondtubular member 30 to serve as the opposite insert can be positioned onmandrel 32 as indicated by arrow 34. The tubular member 30 will usuallyhave a cylindrically shaped borehole 36. The mandrels 24 and 32 have endportions 38 and 40 respectively which closely receive the boreholes 28and 36 of the respective tubular members 22 and 30 so as to maintain thedesired shape of the borehole in the final product. All corners on theend portions 38 and 40 are preferably rounded to avoid locations highlyprone to failure in the articles produced.

The mandrel end portion 38 having the tubular member 22 mounted thereonis positioned in a portion of a mold cavity 42. In the embodiment of theinvention illustrated in FIG. 2, cavity 42 is determined between a pairof mold blocks 44 and 46 having matching faces 48 and 50 respectively.The block 44 is provided with channels 52 and 54 to receive the mandrels24 and 32 respectively. The block 46 is provided with similar channelsnot numbered. Register means 56 and 58 are provided on the mandrels 24and 32 respectively for engagement with registry receipts in the blocksto position the mandrels 24 and 32 during the molding operation.

The remainder of the mold cavity 42 (not occupied by the shafts 24 and32 having tubular members 22 and 30 thereon) is filled with fiberreinforced thermoplastic matrix preferably so that the completed articleis predominantly reinforced with random fibers. In the embodiment of theinvention illustrated in FIG. 2, which is a stamp mold, the preferredtechnique for this step is as follows. Smooth blank composite sheets cutand weighed for correct size, are loaded onto a conveyor screen whichthen moves through an infrared oven. After the correct moldingtemperature has been reached (usually 25°-100° F. above the softeningpoint of the resin, 600°-650° F. for PPS), the blanks, now roughtextured, exit the heating system and are quickly transferred to themold cavity 42. The mold can be heated if desired. In the case of PPS,the mold is preferably at a temperature in the range of 200°-300° F. Afirst portion of the heated blank charge to the mold is positioned in alower portion of the mold cavity 42. The mandrels and inserts arepositioned. The remaining portion of the heated blank charge to the moldis positioned on the top of the mandrels and inserts. An article in theshape of the mold cavity 42 which has the tubular members 22 and 30encapsulated therein is then produced. In the embodiment of theinvention illustrated in FIG. 2 the article is stamp molded. Theinvention could be practiced in an injection molding apparatus, notshown, if desired. The molded article in the stamp mold is then heldunder pressure (2-6,000 psi) by a mechanical or hydraulic press (closingspeed of greater than 200 in/min., generally 200-700 in/min) until thearticle has cooled sufficiently to retain its shape. This generallyrequires less than about 2 minutes. The article is then removed from themold cavity 42. The mandrels 24 and 32 are removed from the article thusdefining at least one borehole in the article which is reinforced withoriented filaments such as filament windings.

Preferably, the article is molded utilizing a press molding technique.The blank composite sheets are preferably reinforced with random fibermat to provide for fiber flow to all portions of the article during themolding procedure. The blanks generally comprise in the range of about40 to about 70 wt, % of fiber. However, the invention can also bepracticed to produce an injection molded article in which case the moldcavity will be filled with a thermoplastic matrix which is reinforcedwith short random fibers. By short is meant fibers having a length of 1cm or less, usually in the range of from about 0.01 up to about 1 cm.Suitable injection molding compound will generally contain in the rangeof 10 wt, % to 50 wt, % of reinforcing fiber. Either way, the moldcavity is brought up to sufficient pressure, in the case of stampmolding generally from about 2,000 to about 6,000 psi, to cause thethermoplastic of the tubular member 22 and the thermoplastic materialwith which the remainder of the mold cavity 42 has been filled to forman integral thermoplastic matrix throughout the article.

The article produced according to the invention can be used as the valveelement in a butterfly valve, for example, to control fluid flow.

That which is claimed is:
 1. A valve element for controlling fluid flowin a butterfly valve comprising:(a) a flattened disk-like member havingan outer circumference and comprised of a thermoplastic polymer matrixcontaining random fiber reinforcement. (b) said disk-like member havinga channel defined therein, said channel being diametrically extendingand having side walls extending radially inward from said outercircumference, said disk-like member being transversely thickened in theregion of said channel, and (c) a tubular sleeve insert member (1)comprised of a thermoplastic polymer matrix containing filament woundfiber, (2) having circumferential walls defining outside and insidecircumferential wall surfaces, and (3) located matingly in, andintegrally associated with, said channel, (d) said circumferential wallsbeing noncylindrical and said channel so associated therewith having itssaid side walls matingly configured thereto.
 2. A valve element as inclaim 1 wherein said random fiber reinforcement is predominantly randommat and said opposed channels are separate.
 3. A valve element as inclaim 2 wherein said thermoplastic polymer in said disk-like member andsaid thermoplastic polymer in said at least one insert is selected fromthe group consisting of polyethylene, polypropylene,polytetrafluoroethylene, polyamide and poly(arylene sulfide).
 4. A valveelement as in claim 3 wherein each of said random and said filamentwound fiber reinforcement is selected from the group consisting ofcarbon fiber and glass fiber.
 5. A valve element as in claim 4 whereinsaid inside circumferential wall of said at least one tubular insertdefines a bore, wherein said inside surface is noncylindrically shapedso as to provide engagement with a shaft when inserted into said bore.6. A valve element as in claim 5 wherein said inside surface ischaracterized by at least one pair of opposed flats.
 7. A valve elementas in claim 6 comprising in addition a second tubular sleeve insertmember, said second tubular sleeve insert member:(1) being comprised offilament wound fiber reinforcement in a thermoplastic matrix, (2) havingcircumferential walls defining outside and inside circumferential wallsurfaces, and (3) being located matingly in, and integrally associatedwith, said second channel.
 8. A valve element as in claim 7 wherein saidthermoplastic polymer in said disk-like member and said thermoplasticpolymer in said at least one insert comprises a poly(phenylene sulfide).9. A disk element for controlling fluid flow in a butterfly valvecomprising:(a) a flattened disk-like number comprised of a fiberreinforced thermoplastic polymer and having an outer circumference, (b)said disk-like member having a pair of diametrically opposed channelsdefined therein, each said channel having side walls radially inwardlyextending from said outer circumference, said disk-like member beingtransversely thickened in the regions of said channels, and (c) a pairof tubular sleeve insert members, each said insert member(1) beingcomprised of poly(arylene sulfide) reinforced with fibers selected fromthe group consisting of carbon fibers and glass fibers, (2) havingcircumferential walls defining outside and inside circumferential wallsurfaces, and (3) being located matingly in, and integrally associatedwith, a different one of said channels, (d) said circumferential wallsof at least one of said insert members being cross-sectionallynon-circular and said channel so associated therewith having its saidside walls matingly configured thereto.